/**
 * 用户登录
 **/
sun.login = function(loginInfo, callback) {
	callback = callback || $.noop;
	loginInfo = loginInfo || {};
	loginInfo.account = loginInfo.account || '';
	loginInfo.password = loginInfo.password || '';
	var ref = sun.createLink("/user");
	ref.once("value", function(snapshot) {
		var result = snapshot.val();
		mui.each(result, function(key, elem) {
			if(elem.account == loginInfo.account &&
				elem.password == loginInfo.password) {
				callback(elem);
			}
		});
	});
}